1. Field of Invention
The present invention relates to energy-activated room temperature-pumpable polymer compositions and devices for activating and dispensing the same to form solid cellular or solid non-cellular polymeric materials.
2. Description of Related Art
In conventional systems for dispensing hot melt adhesives, solid thermoplastic pellets of hot melt adhesive composition are conveyed to a hot melt pot or kettle. The pellets are heated, in bulk, in the kettle to a temperature above the melting temperature of the hot melt adhesive composition. The molten hot melt material in the kettle is pumped in a heated state through heated hoses or lines to a plurality of heated remote dispensing devices, which are typically, located a significant distance away from the kettle.
There are several drawbacks with the use of conventional hot melt dispensing systems. For example, there is a significant energy cost involved in melting a bulk amount of the hot melt composition within the kettle and also in conveying the molten material through the heated lines to the heated dispensing equipment. A stability failure of the of the adhesive, sealant, coating or gasketing material and/or heating system can result in plugged lines and significant down time. In addition, unpleasant odors and smoke typically emanate from the kettle. The heated kettle and the heated hoses present safety hazards within the workplace. Furthermore, the complexity of the system makes difficult and time consuming to service and replace equipment. And, the need to maintain the hot melt adhesive at high temperature for extended periods of time tends to lead to a degradation of the composition and its adhesive properties.
Stumphauzer, et. al., U.S. Pat. No. 7,285,583 (hereinafter “the '583 patent”), the specification of which is hereby incorporated by reference in its entirety, discloses a multiple component polymer composition that is pumpable at room temperature, but which forms a molten hot melt composition when heated above about 300° F. and mixed. The molten hot melt composition can be dispensed to form a solid adhesive material upon cooling. This patent discloses that the composition can include “foaming agents”, such as azobisdicarbonamide, for the purpose of generating foam in the molten hot melt composition, which expands the volume and reduces the density of the solid adhesive. Azobisdicarbonamide liberates nitrogen gas when heated. Nitrogen gas is considered to be a non-reactive blowing agent.
Stumphauzer, et. al., U.S. Pat. No. 7,221,859 (hereinafter the '859 patent”), the specification of which is hereby also incorporated by reference in its entirety, discloses a device that can be used to heat a multiple component polymer composition such as disclosed in the '583 patent from its pumpable room temperature state to a temperature at which the material becomes a molten liquid. The device statically mixes the molten liquid, which converts it to a hot melt as it exits from the device into commercially available hot melt dispensing heads. Once the molten material is dispensed from the dispensing head, the material exhibits adhesive properties that are substantially similar to conventional packaging hot melt.